Among slide-type cellular telephone sets consisting of an upper case, a lower case and a coupling section, a conventionally known cellular telephone set is one having a configuration where an antenna is provided in the vicinity of the coupling section of the lowercase, and the antenna is extended associated with an operation to extend the case when the case is opened, and is housed associated with an operation to house the case when the case is housed. With such a configuration, since a trouble of extension/retraction of the antenna is saved and the antenna is extended without fail in use of the cellular telephone set, it is possible to secure a conversation without provision of a protruded portion, so as to reduce a thickness of the set (Japanese Patent Unexamined Publication No. 2003-298695).
However, in the slide-type cellular telephone set described in Japanese Patent Laid-Open No. 2003-298695, although it is possible to realize reduction in size and enhancement in usability, there has been a problem with the configuration and position of the antenna in order to stably secure high quality antenna performance in either the extended or housed states.